1. Field of the Invention
This invention relates to high pressure pneumatically operated valves and more particularly to such valves which can also be operated manually and can be locked in the closed position. Such valves are particularly suitable as compressed gas cylinder valves.
2. Background Information
High pressure valves for compressed gas cylinders have typically been manually operated. In a common type of manually operated high pressure compressed gas cylinder valve, an inner valve stem is spring biased open with respect to a seat formed in the valve body at an inlet from the gas cylinder. The valve is closed by rotating an outer valve stem axially aligned with the inner stem and threadedly received in the valve body to move the inner stem against the spring bias until it creates a seal against the valve body seat. A set of diaphragms between the outer and inner valve stems forms a gas tight seal for the stem. The valves are protected during transportation and storage by a cylindrical transport cap with a hemispherical end which encloses the valve and screws onto a threaded neck on the gas cylinder.
Such valves have proven that they can be operated easily and safely and can remain leak tight for the thousands of cycles. They have performed satisfactorily in hostile environments with high pressure corrosive, toxic, flammable and pyrophoric gases.
It has been found that for certain uses, such as in the semiconductor industry, it is desirable to be able to open and close compressed gas cylinder valves more rapidly than can be accomplished manually and also to be able to control the flow of the compressed gas remotely. At the same time leak integrity requirements are more stringent for such applications and tighter gas purity requirements necessitate cleaner valves as well as cylinders.
It is, therefore, a primary object of the invention to provide a high pressure compressed gas cylinder valve which can be opened and closed rapidly, but which is leak tight, and is easy to keep clean.
It is another object of the invention to provide such a valve which is pneumatically operated.
It is yet another object of the invention to provide such a pneumatically operated valve which can also be operated manually.
It is still another object of the invention to provide such a valve which can be locked in the closed position for storage and travel.
It is another important object of the invention that the present manually operated high pressure valves can be easily converted to pneumatically operated valves which can be manually opened and locked in the closed position.
It is yet another object of the invention that such valves be usable with existing transport caps.